I think you can formulate your question better. You're trying to ask many questions in one statement, it feels like.
SNES samples are always in
BRR format. The output from the system is always 16-bit stereo PCM, 32khz.
The sample rate of each individual sample depends on the pitch. If you use SPCPlay you can see the raw pitch values sent to the DSP, if you go Settings >Information > Channel 1. The pitch values are represented in hex, convert to decimal and multiply by 7.8125 for the sample frequency in Hz.
In general, it's impossible to see the quality of each individual sample if you only have the mixed output. The best you can do, is to isolate the sample (find some sound bit where no other sample is playing) and do a FFT spectrum analysis, but even this is imperfect if there is additional processing.